Remotely operable explosive plug insertion tool

ABSTRACT

A spring-loaded insertion tool for carrying and inserting an explosive plug for repairing tubes in a nuclear steam generator. The tool is comprised of a movable clamp support having an expansion clamp mounted thereon. The expansion clamp has a pair of flanged protuberances extending therefrom which engage the explosive plug. Spring loaded jaws for opening and closing the expansion clamp are pivotally attached to the clamp support. A control plunger is remotely operable to open and close the spring loaded jaws. A counterbalance weight is attached to the clamp support to maintain the explosive plug in a predetermined orientation while the plug is carried to the appropriate tube in the nuclear steam generator.

45711 KR 321863is97 United States Patent [1 1 3,863,976

L h 1 Feb. 4, 1975 [54] REMOTELY OPERABLE EXPLOSIVE PLUG 3,654,686 4/1972 McFarland et a1 294/19 R X INSERTION TOOL 75 Inventor: Emil P. Loch, Tampa, Fla. Jr

r [73] Assignee: yestgnghloui e Electric Corporation, Attorney, A or F G H T lf ltts urg a.

[22] Filed: Feb. 12, 1973 [57] ABSTRACT [21] Appl. No.: 331,459 A spring-loaded insertion tool for carrying and inserting an explosive plug for repairing tubes in a nuclear steam generator. The tool is comprised of a movable [52] 294/97 294/19 3 35 8 clamp support having an expansion clamp mounted 51] l t Cl B25b/5/l2 thereon. The expansion clamp has a pair of flanged 93 9 protuberances extending therefrom which engage the le 0 care 8, e plosi e loaded jaws for opening and 294/8624 19 86 99 115 closing the expansion clamp are pivotally attached to the clamp support. A control plunger is remotely op- [56] References Cited erable to open and close the spring loaded jaws. A

UNITED STATES PATENTS counterbalance weight is attached to the clamp sup- 1,776,776 9/1930 Blackmarr 294/97 X port to maintain the explosive plug in a predetermined orientation while the plug is carried to the appropriate tube in the nuclear steam generator.

Le Vesque H 294/19 R 7 Claims, 9 Drawing Figures PATENTED FEB 4 I975 SHEET 2 0F 3 PATENTEU FEB 4 75 sum 3 or FIG. 4.

REMOTELY OPERABLE EXPLOSIVE PLUG INSERTION TOOL BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to nuclear steam generators, and in particular, to an explosive plug insertion tool utilized in the repair of a nuclear steam generator.

2. Description of the Prior Art During operation steam generator tubes develop leaks at various points throughout the active length of such tubes. Suchleaks usually necessitate a plant shutdown to repair the leaking tube. In the past, this repair has usually required that a workman enter the channel head of the steam generator and insert an explosive plug into the appropriate tube to seal the tube and, in this manner, stop the leak.

This technique has been utilized to repair leaking tubes in a nuclear steam generator. However, since the radioactivity level within a nuclear steam generator is high, current safety standards limit the time a workman can safely operate within a radioactive area, such as the channel head of the nuclear steam generator. Consequently, the plugging of a multiplicity of leaking tubes in a nuclear steam generator requires a number of workmen in order to insure that each individual workman is not exposed to an excessive dose of radiation. The repair process is therefore expensive and time consuming.

This invention provides a tool for remotely inserting the explosive plug into the appropriate tube from outside the channel head. The tool disclosed in this invention will enable a workman to remotely insert the explosive plug without physical entry into the channel head of the nuclear steam generator. The tool is capable of supporting an explosive plug of thecurrent art without requiring a change in the plug itself. In addition to safety, practicality and weightare prime considerations involved. The tool must be capable of reaching all the tubes within a given tube plate. Also, the tool must be of lightweight construction so that the plug may be inserted into the appropriate tube and released prior to detonation with a minimum effort by the workman.

I SUMMARY OF THE INVENTION The tool head disclosed by this invention accomplishes the aforementioned requirements. The tool head is capable of supporting existing explosive plugs without requiring a change inthe plug itself. The tool is fabricated of durable, lightweight aluminum and provides a rigid support for the explosive plug. The tool is capable of reaching all the tubes within a given tube plate, and the explosive plug may be inserted with a minimum of effort. Once inserted, the plug and detonator cord are easily released from the tool and left in position ready for detonation.

The tool head is comprised of a movable clamp support having an interchangeable, removable, expansion clamp mounted thereon. The expansion clamp is available in a plurality of sizes, so that the tool head is easily adapted for use with any one ofa predetermined number of explosive plug sizes. The expansion clamp has two corresponding flanged protuberances extending therefrom which fit into the interior cavity of the standard explosive plug.

Spring loaded means for opening and closing the expansion clamp are connected to the clamp support by linking means. The clamp support is pivotally mounted on the linking means. A control plunger for operating the spring loaded means is carried by an elongated control rod. A spring biases the expansion clamp toward the open position.

A counterbalance is provided to maintain the clamp support and the explosive plug in a predetermined orientation, despite the orientation of the tool head and the control rod.

The tool head is light in weight, being fabricated'of aluminum, and allows easy insertion of an explosive plug without exposure of the operator to excessive radiation levels.

An object of the invention is to provide a remotely operable explosive plug insertion tool so that an explosive plug may be inserted into a leaking tube welded to a tube plate ofa nuclear steam generator without physical entry into the channel head: of the nuclear steam generator.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more fully understood from the following detailed descriptionof an illustrative embodiment taken in connection with. the accompanying drawings, inwhich:

FIG. 1. is a sectional view of a nuclear steam generator, channel head showing the utilization ofa tool head described by this invention;

FIG. 2 is a top view of a toolhead constructed according to the teachings of the invention;

FIG. 3 is an isolated top view ofa clamp support pair utilized in the invention;

FIG. 4 is anisolated elevational view of a clamp support pair taken along line lV-IV in FIG. 3;

FIG. 5 is anisolated top view of an expansion clamp pair utilized in the invention;

FIG. 6 is an isolated elevational view of an expansion clamp pair, taken along line VI-VI in FIG. 5;

FIG. 7 is an elevational view partially in section, of a tool head utilizing the-teachings of the invention, taken along section line. VII-VII of FIG. 2;

FIG. 8 is a top view similar to FIG. 2, illustrating a tool head in a closed, second position; and

FIG. 9 is a sectional view of a typical explosive plug.

DESCRIPTION OF THE PREFERRED EMBODIMENT Throughout the following description, similar reference characters refer to similar elements in all figures of the drawings.

Referring now to the drawings and to FIG. 1 in particular, a sectional view of a nuclear steam generator 10, and in particular, a channel head 12 of the nuclear steam generator 10, showing the utilization of the invention, is illustrated.

The channel head 12 has an inlet chamber 14 and an outlet chamber 16 therein. A partition sheet 18 separates the inlet chamber 14 from the outlet chamber 16. The channel head 12 has an inlet nozzle 20 therein, the inlet nozzle 20 communicating with the inlet chamber 14. A tube sheet 22, having a plurality of tubes 24 ending therein, is disposed within the channel head 12.

The channel head 12 has a plurality of manways 26. The manways 26 are disposed so that each of the tubes 24 in the tube sheet 22 is accessible from the interior of the channel head 12 by utilization of one of the plurality of manways 26. However, only one of the plurality of manways 26 is illustrated.

During operation of the nuclear steam generator the tubes 24 may develop leaks at various points in the active length of the tube 24. In the past, in order to repair such leaks, the entire system was shutdown and a workman entered the appropriate manway 26 into the channel head 12 and inserted an explosive plug into the tube 24 that was to be sealed. Upon insertion of the plug, the workman withdrew from the chamber, the plug was detonated and the tube sealed.

However, this repair technique is not able to be utilized with the nuclear steam generator 10 because of the excessive radiation levels within the channel head 12. These radiation levels limit the periods during which a workman can safely work within the channel head 12 without being exposed to an excessive dose of radiation.

The invention discloses a tool head 28 which is mounted on an extension rod 29 and which will permit installation of an explosive plug 30 into the appropriate tube 24 without necessitating physical entry into the channel head 12. The explosive plug 30 is mounted on the tool head 28. The tool head 28 is inserted through the appropriate manway 26 and guided by the extension rod 29 to the appropriate tube 24. The explosive plug 30 is then inserted into the tube 24 and the extension rod 29 and tool head 28 are withdrawn. The explosive plug 30 is then remotely electrically detonated by use of a detonator cord 31 and electrical detonator.

It is thus seen that utilization of the tool head 28 provides a method of inserting an explosive plug into a leaking tube in a nuclear steam generator without necessitating the physical entry of a workman into the channel head of the nuclear steam generator, thus avoiding any danger of exposure of the workman to the radiation levels within the channel head.

Referring now to FIG. 2, a top view ofa tool head 28 utilizing the teachings of the invention is illustrated. The tool head 28 is comprised of a movable clamp support pair 32 having a removable expansion clamp pair 34 mounted thereon. Means 36 for moving the clamp support from a first, normally open, position to a second, closed position are connected by linking means 38 to the movable clamp support pair 32. A spring 40 biases the movable clamp support pair 32 toward the normally open first position illustrated in FIG. 2.

Referring now to FIGS. 3 and 4, FIG. 3 illustrates an isolated top view of the movable clamp support pair 32 while FIG. 4 is a view taken along lines IV-IV of FIG. 3. The movable clamp support pair 32 is comprised of a first clamp support member 42 and a second clamp support member 44 linked by a connecting and aligning member 46. The connecting and aligning member 46 fits into a notch 48 cut into each clamp support member and is secured to the first clamp support member 42 by pins 50. The connecting and aligning member 46 insures that the first clamp support member 42 and the second clamp support member 44 will remain aligned with each other during utilization of the tool head 28.

The first clamp support member 42 has a leading edge 51 and a substantially semicircular groove 52 therein. The second clamp support member 44 has a leading edge 53 and a corresponding semicircular groove 54 therein. The juxtaposition of the first clamp support member 42 and the second clamp support member 44 defines a substantially circular channel 56 which extends between the first clamp support member 42 and the second clamp support member 44. When the explosive plug 30 (FIG. 1) is carried by the tool head 10, the detonator cord 31 extends through the circular channel 56 between the first clamp support member 42 and the second clamp support member 44. Juxtaposition of the leading edge 51 ofthe first clamp support member 42 and the leading edge of the second clamp support member 44 defines a substantially wedge-shaped channel 57 that extends between the first clamp support member 42 and the second clamp support member 44. The wedge-shaped channel 57 communicates with the circular channel 56 through a clearance space 58. The clearance space 58 and the wedge-shaped channel 57 provide an escape route for the detonator cord 31 (FIG. 1). After the explosive plug 30 is inserted into the appropriate tube 24, the detonator cord 31 passes from the circular channel 56 into the wedge-shaped channel 55 through the clearance space 58. Release ofthe detonator cord 31 in this manner prevents tangling or displacement of the detonator cord 31 which could result in plug misfire.

Referring now to FIG. 5, an isolated top view of the removable expansion clamp pair 34 utilized in the invention is illustrated. The removable expansion clamp pair 34 is comprised of a first expansion clamp member 62 and a second expansion clamp member 64. The first expansion clamp member 62 has a flat bed portion 66 thereon. A flanged protuberance 68 extends upward from the flat bed portion 66 of the first expansion clamp member 62 (FIG. 6). The second expansion clamp member 64 has a flat bed portion 70 thereon, and a flanged protuberance 72 extending upward from the flat bed portion 70 of the second expansion clamp member 64.

.Iuxtaposition of the first expansion clamp member 62 and the second expansion clamp member 64 defines a substantially circular area of a diameter 74 extending between the flanged protuberance 68 on the first expansion clamp member 62 and the flanged protuberance 72 on the second expansion clamp member 64.

The first expansion clamp member 62 and the second expansion clamp member 64 are fabricated of stainless steel. The removable clamp member pair 34 provides a shield between the explosive plug 30 and the movable clamp support pair 32.

One advantage of utilization of the removable expansion clamp pair 34 having the first expansion clamp member 62 and the second expansion clamp member 64 is to provide the tool head 28 with the capability of carrying the explosive plug 30 having one of a variety of predetermined diameters. Utilization of a different pair of first and second expansion clamp members 62 and 64, having a different distance 74 therebetween, permits the tool head 28 to carry and insert a wide range of explosive plugs 30 having predetermined diameters with minor modifications to the tool head 28 itself.

The removable expansion clamp pair 34 is mounted on the movable clamp support pair 32 by mounting the first expansion clamp member 62 on the first clamp support member 42 by suitable means, illustrated in FIG. 2 by bolts 76, and mounting the second expansion clamp member 64 onto the second clamp support member 44 by suitable means, illustrated in FIG. 2 by bolts 78.

It is thus seen that utilization of the teachings of this invention will provide a tool head for carrying and inserting a plurality of explosive plugs of predetermined diameters by interchanging the appropriate pairof expansion clamps 34 on the movable clamp support pair 32.

Referring again to FIG. 2, the linking means 38 comprises a first connecting rod 80 and a second connecting rod 82. The first clamp support member 42 is pivotally attached to the first connecting rod 80 by a pivot pin 84. The second clamp support member 44 is pivotally attached to the second connecting rod 82 by a pivot pin 86.

The means 36 for opening and closing the clamp support pair 32 cmprises a first tong jaw 88 and a second tong jaw 90. The tong jaws 88 and 90 are pivotally mounted by pins 92 and 94 respectively to a sleeve 96. The extension rod 29 is received by the sleeve 96. The extension rod 29 has a movable plunger 98 therein, the plunger 98 having a head 98A thereon. The plunger 98 is remotely operable.

The means 36 for moving the clamp support 32 from the first, normally open position to the second, closed position further comprises a linkage having a first link 100, a second link 102 and a third link 104. The first link 100 is pivotally attached to the first tong jaw 88 by a pin 106. The second link 102 is pivotally mounted on the second tongjaw 90 by a pin 108. The third link 104 is pivotally mounted to the first link 100 by a pin 110 and pivotally mounted to the second link 102 by a pin 112.

The first tong jaw 88 is rigidly affixed to the first connecting rod 80 by screws 114. The second tong jaw 90 is rigidly affixed to the second connecting rod 82 by screws 116.

The movable clamp support pair 32 is biased in the normally open first position, illustrated in FIG. 1, by the spring 40. The spring 40 is supported by a bolt 118 extending between the first connecting rod 80 and the second connecting rod 82. A washer 120 supports the spring 40 against the second connecting rod 82. The spring 40 is adjustably controlled by a nut 124 mounted on the bolt 118.

The cylindrical sleeve 96 receives the elongated control rod 29 which carries the plunger 98. A spring loaded retainer assembly 126 secures the elongated control rod 29 rigidly into operating position within sleeve 96. The plunger 98 cooperates with the linkage 100, 102 and 104 to move the movable clamp support set 32, (and thus the expansion clamp set 34) from the normally open position to the closed position. The method of operation of tool 28 is discussed in more detail herein.

All components of the tool head 28 are fabricated of a strong, lightweight material, such as aluminum, to provide an easy-to-handle tool head 28. The first expansion clamp member 62 and the second expansion clamp member 64 are, as previously mentioned, fabricated of a shielding material such as stainless steel, to prevent contact between the aluminum tool head 28 and the explosive plug 30.

Referring now to FIG. 7, a view taken along line VII- VII of FIG. 2 is illustrated. The control rod 29 is shown inserted within the sleeve 96. The control rod 29 is secured by the spring loaded retainer assembly 126. The retainer assembly 126 houses a spring loaded generally U-shaped latch 128. Springs 130 provide a bias force on'the latch 128. The springs 130 are secured within the retainer assembly 126 by guide screws 131. The retainer assembly 126 is affixed to the sleeve 96 by screws 132. The latch 128 must be manually operated to receive the extension rod 29. Serrated sides 133 on the latch 128 are provided to assist and secure manual grip.

The second tong jaw 90 is pivotally attached to the sleeve 96 by the pin 94. The second link 102 is pivotally attached to the second tongjaw 90 by the pin 108. The second link 102 is pivotally attached to the third link 104 by the pin 112. The second tong jaw 90 is rigidly affixed to the second connecting rod 82 by the screws 116. The bolt 118 supports the bias spring 40 between the first connecting rod and the second connecting rod 82. The first connecting rod 80 is pivotally attached to the first clamp support member 42 by the pivot pin 84.

The first expansion clamp member 62 is mounted on the first clamp support member 42 by the bolts 76. The flat bed portion 66 and the flanged protuberance 68 of the first expansion clamp member 62 are shown.

A shaft 132A is threaded into an opening 134 in the underside of the first clamp support member 42. The shaft 132 has a weight 134 mounted on the shaft 132 and secured by nuts 136 and 138. A nut 140 secures the shaft 132 into the opening 134.

Since the first clamp support member 42 is pivotally mounted to the first connecting rod 80, the weight 134 provides the counterbalance means for maintaining the first clamp support member in a predetermined orientation. A similar counterbalance (not shown) is provided for the second clamp support member 44, thus maintaining the second clamp support 44 in a predetermined orientation. The connecting and aligning member 46 insures that the first clamp support member 42 and the second clamp support member 44 will remain aligned with each other, thus preventing independent rotation of one of the clamp support members with respect to the other. The weights disposed on the underside of the aligned clamp support members insure that the explosive plug 30 (FIG. 1) will remain in a predetermined orientation, despite the orientation of the tool head 28 or the extension rod 29, while the plug 30 is being carried to the appropriate tube 24.

Referring now to FIG. 8, a top view of the tool head 28 in the closed, second position, is shown. The extension rod 29 carries the plunger 98. In the closed second position, the plunger 98 and the plunger head 98A thereon are extended forward of its previous position (FIG. 2). The extended plunger 98 exerts a force on the third link 104 which causes the third link 104 to be displaced forward of the position occupied in the first,-

normally open, position (FIG. 2). Displacement of the link 104 displaces the pivotally attached links 100 and 102 and exerts a force on the first tong jaw 88 and the second tong jaw causing the tong jaws 88 and 90 to converge toward each other in a direction indicated by arrows 142 and 144.

Convergence of the first tong-jaw 88 and the second tong-jaw 90 moves the first connecting rod 80 and the second connecting rod 82 closer together against the force exerted by the spring 40. Closing of the connecting rods 80 and 82 causes the leading edge 51 of the first clamp support member 42 to converge toward the leading edge 53 of the second clamp support 44, as indicated by arrows 146 and 148. Convergence of the first clamp support member 42 and the second clamp support member 44 causes the distance 74 between the flanged protuberance 68 and the flanged protuberance 72 to narrow, as indicated by numeral 74.

Referring now to FIG. 9, a sectional view of the typical explosive plug 30 is shown. The plug 30 has a central axial cavity 150 with a predetermined diameter 152 extending axially through a portion of the plug 30. When the flanged protuberances 68 and 72 are brought into closer proximity indicated by the distance 74 in FIG. 8, the diameter 152 of the explosive plug 30 is greater than the distance 74 between the flanged protuberances 68 and 72, thus allowing the explosive plug 30 to be mounted onto the flanged protuberances 68 and 72 of the expansion clamp 34.

Once the explosive plug 30 has been mounted on the flanged protuberances 68 and 72, plunger 98 is withdrawn, the linkage 100, I02 and 104 returns to its first, open position, and the spring force 40 impels the connecting rods 80 and 82 toward the open position. The clamp support pair 32 and the expansion clamp pair 34 return to the normal first position, causing the flanged protuberances 68 and 72 to exert an expansion force on the interior of the explosive plug 30 in directions illustrated by arrows 156 and 158, thus rigidly securing the explosive plug 30 on the flanged protuberances 68 and 72, as shown in FIG. 9.

The counterbalance weights 134 provide the necessary force to maintain the explosive plug 30 in the predetermined orientation while carried by the tool head 28 despite the orientation of the control rod 29 and the tool head 28.

Once the explosive plug 30 has been inserted into the appropriate tube 24, the flanged protuberances 68 and 72 are again closed in a manner exactly similar to that described previously. The flanged protuberances 68 and 72 are then withdrawn from the plug 30, leaving the plug 30 inserted in the tube 24. The detonator cord 31, which extended through the circular channel 56 (FIG. 3) between the first clamp support member 42 and the second clamp support member 44 while the plug 30 was carried into position, is permitted to escape through the clearance space 58 and the wedge-shaped channel 57 between the clamp support members 42 and 44. The plug 30 is then remotely detonated.

It is thus seen that this invention provides a strong, lightweight flexible tool head for carrying and inserting an explosive plug into a leaking tube in a tube plate of nuclear steam generator, without requiring the physical entry of an operator into the channel head of the nuclear steam generator.

I claim as my invention:

1. An expansion clamp tool for carrying and inserting an explosive plug having an internal opening therein, said expansion clamp tool comprising:

a movable clamp support;

a movable clamp mounted on said clamp support;

means for moving said clamp support from a first open position to a second closed position, said movable clamp support being pivotally attached to said means; and,

means for biasing said clamp support toward the first open position, said clamp being insertable into said opening in said plug when said clamp support is in the second closed position, said clamp support responding to said bias means to return to said first open position to permit said clamp to hold said plug from within said internal opening.

2. The expansion clamp tool of claim 1, wherein said movable clamp support comprises:

a first clamp support member;

a second claim support member; and

a connecting and aligning member connecting and aligning said first clamp support member and said second clamp support member.

3. The expansion clamp tool of claim 2, wherein said removable clamp comprises:

a first clamp member having a protuberance extending therefrom; and

a second clamp member having a protuberance extending therefrom; said first clamp member being removably attached to said first clamp support member, and said second clamp member being removably attached to said second clamp support member.

4. The expansion clamp tool of claim 1 wherein said means for moving said clamp support comprises:

closing means for moving said clamp support from said first open position to said second closed position, and

linking means attaching said closing means to said clamp support, said clamp support being pivotally attached to said linking means.

5. The expansion clamp tool of claim 1, further comprising means for counterbalancing said clamp support member, said means for counterbalancing said clamp support member exerting a force acting through the pivotal point of attachment of said clamp support to said means for moving said clamp support.

6. The expansion clamp tool of claim 5, wherein said plug has an axis extending centrally and axially through said plug and said internal opening therein,

said movable clamp support comprises a first clamp support member, a second clamp support member,

and a connecting and aligning member connecting and aligning said first clamp support member with said second clamp support member;

said removable clamp comprises a first clamp member having a protuberance extending therefrom, a second clamp member having a protuberance extending therefrom, said first clamp member being removably attached to said first clamp support member, said second clamp member being removably attached to said second clamp support member;

said means for moving said clamp support comprises closing means for moving said clamp support from said first open position to said second closed position, and linking means for attaching said closing means to said clamp support, said clamp support being pivotally attached to said linking means; and,

said means for counterbalancing said clamp support member comprises a first shaft having a weight thereon, said first shaft attached to said first clamp support member and a second shaft having a weight thereon, said second shaft being attached to said second clamp support member,

said first clamp support and said second clamp support members responding to said closing means to move from said first open position to said second closed position, closing of said clamp support members permitting said protuberances on said first and said second removable clamp members to be inserted into said internal opening in said plug, said first and said second clamp support members responding to said bias means to return to said first open position, said movement of said first and said second clamp support members to said first open position extending said protuberances to exert holding forces on said plug from within said internal opening of said plug, said holding forces being directed radially outward relative to said axis of said plug,

said counterbalance force exerted by said counterbalance means acting through said point of pivotal attachment of said clamp support and said linking means maintaining said plug held by said internally member and said second clamp support member. 

1. An expansion clamp tool for carRying and inserting an explosive plug having an internal opening therein, said expansion clamp tool comprising: a movable clamp support; a movable clamp mounted on said clamp support; means for moving said clamp support from a first open position to a second closed position, said movable clamp support being pivotally attached to said means; and, means for biasing said clamp support toward the first open position, said clamp being insertable into said opening in said plug when said clamp support is in the second closed position, said clamp support responding to said bias means to return to said first open position to permit said clamp to hold said plug from within said internal opening.
 2. The expansion clamp tool of claim 1, wherein said movable clamp support comprises: a first clamp support member; a second claim support member; and a connecting and aligning member connecting and aligning said first clamp support member and said second clamp support member.
 3. The expansion clamp tool of claim 2, wherein said removable clamp comprises: a first clamp member having a protuberance extending therefrom; and a second clamp member having a protuberance extending therefrom; said first clamp member being removably attached to said first clamp support member, and said second clamp member being removably attached to said second clamp support member.
 4. The expansion clamp tool of claim 1 wherein said means for moving said clamp support comprises: closing means for moving said clamp support from said first open position to said second closed position, and linking means attaching said closing means to said clamp support, said clamp support being pivotally attached to said linking means.
 5. The expansion clamp tool of claim 1, further comprising means for counterbalancing said clamp support member, said means for counterbalancing said clamp support member exerting a force acting through the pivotal point of attachment of said clamp support to said means for moving said clamp support.
 6. The expansion clamp tool of claim 5, wherein said plug has an axis extending centrally and axially through said plug and said internal opening therein, said movable clamp support comprises a first clamp support member, a second clamp support member, and a connecting and aligning member connecting and aligning said first clamp support member with said second clamp support member; said removable clamp comprises a first clamp member having a protuberance extending therefrom, a second clamp member having a protuberance extending therefrom, said first clamp member being removably attached to said first clamp support member, said second clamp member being removably attached to said second clamp support member; said means for moving said clamp support comprises closing means for moving said clamp support from said first open position to said second closed position, and linking means for attaching said closing means to said clamp support, said clamp support being pivotally attached to said linking means; and, said means for counterbalancing said clamp support member comprises a first shaft having a weight thereon, said first shaft attached to said first clamp support member and a second shaft having a weight thereon, said second shaft being attached to said second clamp support member, said first clamp support and said second clamp support members responding to said closing means to move from said first open position to said second closed position, closing of said clamp support members permitting said protuberances on said first and said second removable clamp members to be inserted into said internal opening in said plug, said first and said second clamp support members responding to said bias means to return to said first open position, said movement of said first and said second clamp support members to said first open position extending said protuberances to exert holding forces on said plug from within said internaL opening of said plug, said holding forces being directed radially outward relative to said axis of said plug, said counterbalance force exerted by said counterbalance means acting through said point of pivotal attachment of said clamp support and said linking means maintaining said plug held by said internally applied, radially outward directed holding forces in a predetermined orientation, said connecting and aligning member maintaining said first and said second clamp support members in a connected and aligned orientation.
 7. The expansion clamp tool of claim 6, wherein said first clamp support member has a semi-circular groove therein, and said second clamp support member has a semi-circular groove therein, the juxtaposition of said first clamp support member and said second clamp support member defining a substantially circular channel extending axially between said first clamp support member and said second clamp support member. 